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The absorber layers of microcrystalline silicon thin-film solar cells with p-i-n structure deposited by plasma-enhanced chemical vapor deposition at 200 °C are characterized regarding the defect density and the recombination lifetime. The characterization is based on a comparison of experimentally determined solar cell characteristics with results from numerical device simulations. Evaluation of the dark reverse saturation current indicates a strong dependence of the recombination lifetime τ on the hydrogen dilution during the deposition. Close to the transition region to amorphous growth, where the highest solar cell efficiencies are observed, τ is maximum within the crystalline deposition regime and equals around 80 ns. The aspect of a spatially varying defect density within the absorber layer is also addressed by numerical simulations. The results from the analysis of the dark current are compared with electron spin resonance data determined on single layers, which allows conclusions to be drawn regarding the capture cross section of the dominant recombination site in microcrystalline silicon.

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Off-axis holography has successfully revealed the built-in potential in highly doped pn-junctions, making holographic phase retrieval in transmission electron microscopy (TEM) a prospective tool for imaging the electrostatic potential in a semiconductor sample or device. The effect of electron-hole pair generation during electron illumination and the presence of defect rich amorphized sample surfaces in a TEM sample on the electrostatic potential is investigated for the test case of an electrically active grain boundary and a pn-junction in silicon by numerical simulation. In the case of the grain boundary, the pair generation in the electron beam leads to significantly increased recombination currents into trap state defects. As a result, the trapped charge in the defects is decreased and the potential drop around the electrically active defect is considerably reduced, for electron-hole pair generation rates typically present in a TEM experiment even below the detection limit of holography. In the case of pn-junctions distorted potential maps are predicted for dopant densities smaller than 10 17 cm −3 .

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